War on Weeds—weeds are everybody’s problem

Hoary Alyssum (Berteroa incana) is tap-rooted annual, biennial or short-lived perennial that is native to Eurasia. It invades dry disturbed soils such as roadsides, lawns, and overgrazed pastures. This plant is toxic to horses, and it reduces the overall feed value for other livestock. 

Hoary alyssum, a member of the mustard family, can grow up to 3 feet tall. Grayish star-shaped hairs cover the plant giving it a grayish-green (hoary) appearance. Lower leaves can be up to 2 inches in length and are widest towards the tips, upper leaves are similar but much smaller. It has small white flowers, each containing 4 deeply divided petals, making it look like there are 8 petals. Horry alyssum produces seed for much of the growing season. Each plant can produce up to 2,500 seeds per year, which can remain viable for up to 9 years. Seeds are gray-brown and oblong shaped. Seeds are easily spread by wildlife, humans, contaminated hay, and vehicles.

Integrated Pest Management (IPM)

Options: 

Prevention— Learn to identify this plant. Plant certified seed.

Mechanical— Hand digging can be an effective way to remove small infestations, remove as much of the root system as possible to prevent regrowth. Mowing can be an effective method used to keep this weed from going to seed (may have to mow multiple times a year).

Cultural— Maintaining healthy plant communities will help suppress Hoary alyssum. 

Chemical— 2,4-D amine and Metsulfuron (Escort and others) are herbicide active ingredients that can effectively control this weed. Multiple applications might be necessary to control weeds as they germinate. Only apply Metsulfuron (Escort and others) to pasture, rangeland, and non-crop land. Apply herbicides in the spring prior to bolting of rosettes.  Always read and follow herbicide label directions.

Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou and Bear Lake Counties. 208-547-3205 [email protected]